1. Field Of The Invention
The present invention predominately relates to flexographic printing processes. More particularly, the invention relates to a process for uniformly applying a water-based color coating or ink to the entire surface area of a paper web side which represents the material supply for a converting apparatus such as an envelope machine.
2. Description Of The Prior Art
Large numbers of stationery users require or desire colored envelopes and/or letter sized paper. For standardized colors, sizes and shapes, colored stationery needs are met with colored paper in which the colorant is blended with the paper stock before a web therefrom is laid on a papermachine. By this process, economics require large orders and inventories of a given paper color.
Small orders of uniquely colored envelopes are particularly difficult to meet, economically. Traditionally, such envelopes have been manufactured from white, substantially uncoated paper by a process which includes a flexographic print coating of the envelope machine supply web with a coating of solvent based ink: except in those areas where the envelope gum or adhesive is to be applied. This exception was necessary to accommodate the fact that the usual non-toxic envelope gums will not adhere to solvent ink coated surfaces.
Notwithstanding the gum adherence difficulty with solvent ink, water-based inks have not been used in these applications due to the curling consequences of water-based ink upon the web. Envelope machines are extremely critical with requirements of a flat, uniform web surface. Excess water vehicle absorbed by the web from the prior art water-based inks made the supply web warp, wave and curl.
It is, therefore, an object of the present invention to teach a water-based ink formulation and process of applying it that will not curl or distort a substantially uncoated paper web.
Another objective of the present invention is to teach a method of color coating an envelope machine supply web without the necessity of color omitted print areas to accommodate traditional gum adhesives.
Another objective of the present invention is to teach a converting machine supply web coloring process having such economic advantage over solvent based coloring systems as to reduce the ink costs of such colored envelopes by 30%-40%.